Wind speed and wind energy forecast through Kalman filtering of Numerical Weather Prediction model output

This paper presents a review of the current state of the art solutions to the problem of wind farm optimal design. The aim of this work is to present the problem by identifying the most relevant issues involved in the design of a wind farm, as well as to discuss the optimization techniques and wind farm models used in the published literature. An appropriate wind turbine layout is vital in order to obtain adequate performance in relation to the exploitation and operation of the plant during its lifespan. There are several factors that influence wind farm design, chief among them are the calculation of the overall energy yield by the wind farm and the initial investment. The energy produced depends on the local wind conditions and the interference caused by wind turbines nearby. The investment is mainly related to wind turbine acquisition, civil works and electrical infrastructure. However, these are not the only items that influence the design of a wind farm since economic indicators, environmental issues, local regulations, or the presence of wind farms should also be taken into account when deciding the design of the wind farm. Even in the case of the most simplified objective function (maximizing the annual energy produced) the optimization problem cannot be solved by classical optimization techniques. To cope with this problem, most authors have used meta-heuristics techniques which have proved to be efficient when searching for the optimal solution to this problem. The purpose of this paper is to review previous work by offering a clear outline of the latest advances, as well as to highlight the main aspects which need to be taken into account when tackling the wind farm design problem. In addition, in a conclusion of the review, future needs have been identified.

http://www.fglongatt.org/Papers/Paper_Review_MicroSitting_2014.pdf

A review and recent developments in the optimal wind-turbine micro-siting problem

World wind power resources are abundant, but their utilization could be limited because wind fluctuates rather than providing steady power. We hypothesize that wind power output could be stabilized if wind generators were located in a meteorologically designed configuration and electrically connected. Based on 5 yr of wind data from 11 meteorological stations, distributed over a 2,500 km extent along the U.S. East Coast, power output for each hour at each site is calculated. Each individual wind power generation site exhibits the expected power ups and downs. But when we simulate a power line connecting them, called here the Atlantic Transmission Grid, the output from the entire set of generators rarely reaches either low or full power, and power changes slowly. Notably, during the 5-yr study period, the amount of power shifted up and down but never stopped. This finding is explained by examining in detail the high and low output periods, using reanalysis data to show the weather phenomena responsible for steady production and for the occasional periods of low power. We conclude with suggested institutions appropriate to create and manage the power system analyzed here.

https://www.pnas.org/content/pnas/107/16/7240.full.pdf

Electric power from offshore wind via synoptic-scale interconnection

Basic fluid equations are the main ingredient in the development of theories of Rayleigh–Taylor buoyancy-induced instability. Turbulence arises in the late stage of the instability evolution as a result of the proliferation of active scales of motion. Fluctuations are maintained by the unceasing conversion of potential energy into kinetic energy. Although the dynamics of turbulent fluctuations is ruled by the same equations controlling the Rayleigh–Taylor instability, here only phenomenological theories are currently available. The present review provides an overview of the most relevant (and often contrasting) theoretical approaches to Rayleigh–Taylor turbulence together with numerical and experimental evidence for their support. Although the focus is mainly on the classical Boussinesq Rayleigh–Taylor turbulence of miscible fluids, the review extends to other fluid systems with viscoelastic behavior, affected by rotation of the reference frame, and, finally, in the presence of reactions.

/pdf/incompressible-rayleigh-taylor-turbulence-4vptimu7id.pdf

Incompressible Rayleigh–Taylor Turbulence

Combining wind farms with concentrating solar plants to provide stable renewable power

In contrast to conventional power generation, wind energy is not a controllable resource because of its stochastic nature, and the cumulative energy input of several wind power plants into the electric grid may cause undesired fluctuations in the power system. To mitigate this effect, the authors propose a procedure to calculate the optimal allocation of wind power plants over an extended territory to obtain a low temporal variability without penalizing too much the overall wind energy input into the power system. The procedure has been tested over Corsica (France), the fourth largest island in the Mediterranean Basin. The regional power supply system of Corsica could be sensitive to large fluctuations in power generation like wind power swings caused by the wind intermittency. The proposed methodology is based on the analysis of wind measurements from 10 anemometric stations located along the shoreline of the island, where most of the population resides, in a reasonably even distribution. First ...

Optimization of the Regional Spatial Distribution of Wind Power Plants to Minimize the Variability of Wind Energy Input into Power Supply Systems

Following the idea that the climatological study of a physical variable should aim at the comprehension of its mean state as well as the characterization of its dynamics, cluster analysis has been applied to study the wind climate of Corsica (France) in order to identify the anemological regions (mean state) and the wind regimes (weather variability) which characterize its coastal areas. The analysis is based on a 3-year long time-series of measurements of the wind velocity from 11 anemometric stations located along the perimeter of the island. Since the present study was an analysis preliminary to the subsequent assessment of the wind potential of Corsica, we have worked only with wind intensities. Nevertheless, at the end of our analysis, we have also considered wind directions for the final interpretation of the results. The anemological regions are defined through the comparison of 15 different clustering techniques resulting from the combination of three distance measures and five agglomerative methods. As confirmed by geographical considerations, the results identify three distinct anemological regions: the eastern region (ER), the north-western region (NWR), the south-western region (SWR). The wind regimes are identified by means of a two-stage classification scheme based on a hierarchical cluster analysis followed by a partitional clustering. The final classification identifies eight regimes: the four wind regimes corresponding to the main weather patterns of Western Europe, as proposed by Plaut and Simonnet, and another four clusters corresponding to breeze regimes. Copyright © 2007 Royal Meteorological Society

Mesoscale wind climate analysis: identification of anemological regions and wind regimes

Temperature fluctuations in an atmospheric convective boundary layer are investigated by means of large eddy simulations (LESs). A novel statistical characterization for both weak temperature fluctuations and strong temperature fluctuations has been found. Despite the nontriviality of the dynamics of temperature fluctuations, the data presented here support the idea that the most relevant statistical properties can be captured solely in terms of two scaling exponents, characterizing the entire mixed layer. Such exponents control asymptotic (i.e., core and tails) rescaling properties of the probability density functions of equal-time temperature differences Δrθ between points separated by a distance r. A link between statistical properties of large temperature fluctuations and geometrical properties of the set hosting such fluctuations is also provided. Finally, a possible application of these new findings to the problem of subgrid-scale parameterizations for the temperature field in a convective ...

Statistics of Temperature Fluctuations in a Buoyancy-Dominated Boundary Layer Flow Simulated by a Large Eddy Simulation Model.

Turbulent fluctuations of both velocity and temperature fields, issuing from high-resolution large-eddy simulations, have been analyzed in convective boundary layers The numerically simulated flows are strongly anisotropic at large scales: this is due both to the action of buoyancy and to the imposed geostrophic wind Their relative weight is varied so that one experiment’s results are much more convective than the other To properly disentangle anisotropic properties, the authors exploit both standard statistical indicators, like skewness coefficients, and the three-dimensional rotational group decomposition SO(3) Two main conclusions can be drawn First, despite the strong anisotropies at large scales, isotropy is statistically recovered at scales much smaller than the large ones Second, relevant statistical indicators of turbulence such as the scaling exponents, of both velocity and temperature fields, are remarkably close for the two experiments Implications of these findings for the prob

Anisotropies and Universality of Buoyancy-Dominated Turbulent Fluctuations: A Large-Eddy Simulation Study

The Large-Eddy Simulation technique is exploited to investigate statistics of temperature fluctuations, Δ r θ, in Atmospheric Boundary Layers (ABLs) with different degrees of convection. We found statistical characterizations for both strong and weak fluctuations. In terms of probability density functions (pdfs) of Δ r θ, weak and strong fluctuations reflect themselves in different rescaling properties of pdf cores and tails, respectively. For the cores, the observed rescaling is P(Δ r θ) = r −α (Δ r θ/r α); while for the tails, data are compatible with P(Δ r θ)∝ r ζ∞ . Such two rescaling properties are equivalent to saying ⟨|Δ r θ| p ⟩∼ r ζ p , with ζ p = α p for small p's and ζ p = ζ∞ = constant for large p's. Both α and ζ∞ turn out to be z-independent within the mixed layer and, more importantly, they do not appreciably vary by changing the degree of convection in the ABL. We also address the question related to the geometrical structure of temperature jumps contributing to large |Δ r θ|. Finally, the ...

Marta Antonelli

Papers

Optimization of the Regional Spatial Distribution of Wind Power Plants to Minimize the Variability of Wind Energy Input into Power Supply Systems

Mesoscale wind climate analysis: identification of anemological regions and wind regimes

Statistics of Temperature Fluctuations in a Buoyancy-Dominated Boundary Layer Flow Simulated by a Large Eddy Simulation Model.

Anisotropies and Universality of Buoyancy-Dominated Turbulent Fluctuations: A Large-Eddy Simulation Study

Structure of temperature fluctuations in turbulent convective boundary layers